Meta suffered a major defeat on Wednesday that could severely undercut its Facebook and Instagram advertising business after European Union regulators found it had illegally forced users to effectively accept personalized ads.The ruling is one of the most consequential judgments since the 27-nation bloc, home to roughly 450 million people, enacted a landmark data-privacy law aimed at restricting the ability of Facebook and other companies from collecting information about users without their prior consent.The company includes language in its terms of service agreement, the very lengthy statement that users must accept before accessing services like Facebook, Instagram and WhatsApp, that effectively means users must allow their data to be used for personalized ads or stop using Meta’s social media services altogether.Information about a user’s digital history — such as what videos on Instagram prompt a person to stop scrolling, or what types of links a person clicks when browsing their Facebook feeds — is used by marketers to get ads in front of people who are the most likely to buy.judgment is the latest business headwind facing Meta, which was already grappling with a major drop in advertising revenue because of a change made by Apple in 2021 that gave iPhone users the ability to choose whether advertisers could track them."